Linear alkanoates + aromatic hydrocarbon binary mixtures: new excess enthalpy measurements and disquac analysis of thermodynamic properties

Excess enthalpies at 298.15 K and atmospheric pressure are reported for 8 binary liquid mixtures of n-alkanoates (propyl methanoate, butyl methanoate, ethyl ethanoate, propyl ethanoate, butyl ethanoate, methyl propanoate, ethyl propanoate, propyl propanoate) + toluene. These experimental results along with literature data on vapour-liquid equilibrium (VLE), excess molar Gibbs energies (GE), excess molar enthalpies (HE), activity coefficients at infinite dilution (γi∞) and excess molar heat capacities (CpE) of n-alkanoates + benzene, or + toluene are examined on the basis of the DISQUAC group contribution model. The components in the mixtures are characterized by three types of contact surfaces: carboxylate (COO group), aliphatic (CH3 or CH2 groups) and aromatic (C6H6 or C6H5 groups, in benzene or in toluene, respectively). Interaction parameters for aliphatic/aromatic and aliphatic/COO contacts have been estimated previously. In this work, we have determined the missing heat capacity interaction parameters of the aliphatic/COO contact and all the interaction parameters of the aromatic/COO contact. The aromatic/COO contact is best described by entirely dispersive parameters. The Gibbs energy and enthalpy parameters decrease, whereas the heat capacity parameters increase, with the n-alkyl chain of the n-alkanoate.